Auto-injection devices are utilized in a variety of settings, typically to treat medical emergencies. For example, anaphylaxis is a serious medical emergency that can be fatal if not treated quickly. The most common causes of anaphylaxis include food allergies (e.g., nut or shellfish allergies) and insect bites or stings. Certain medications can also cause anaphylaxis. Symptoms of anaphylaxis include an itchy rash, throat swelling, and low blood pressure. Rapid diagnosis and immediate injection of intramuscular epinephrine is often critical to prevent a fatal outcome, as muscles have larger and more blood vessels than subcutaneous tissue and intramuscular injections usually have faster rates of absorption than subcutaneous or intradermal injections. Death from anaphylaxis occurs most often in teenagers and young adults and is directly related to receiving injected epinephrine too late, inaccurately (e.g., outside the muscle), or not at all. Anaphylaxis most often occurs unexpectedly and in the absence of a trained health care professional. Because exposure is unpredictable, the reaction may occur rapidly, and the patient may not be near medical help at the time of exposure, patients who are subject to severe anaphylaxis must carry epinephrine at all times. It is also necessary that the patient be able to self-administer the epinephrine during an anaphylactic attack in an efficient, simple manner.
Currently available auto-injection devices are generally cylindrical in shape and include a spring-activated concealed needle that, when triggered, springs forward to simultaneously pierce the skin and deliver a dose of epinephrine or other medicament. Such devices are designed for single dose intramuscular injection for emergency treatment of anaphylaxis.
Recent studies indicate a number of problems with the aforementioned automatic injection devices. These devices are bulky, difficult to use, and are considered burdensome to the user. Many patients are noncompliant when prescribed these devices and do not carry one with them at all times for various reasons including problems with size, shape and appearance. Further, these devices have a counter-intuitive design that can promote accidental misfiring of a device into the palm of the user's hand rather than into the thigh or other suitable area. In addition, because the dose of epinephrine is delivered at the same time that the needle is injected below the skin in a single step, there is a possibility of injection and dispersion of the epinephrine before the needle reaches the musculature.
Therefore, it can be appreciated that anaphylaxis remains an important and avoidable cause of death and that currently available automatic injection devices have a number of problems associated with their design and function. These problems can contribute to incorrect use, misuse, and not carrying the unit as prescribed (non-compliance), resulting in adverse outcomes.
As such, a need currently exists for an improved auto-injection device for rapid injection of a fluid medicament to the desired location.